1. Field of the Invention
The present invention relates to optical transmitters. More specifically, the present invention relates to optical transmitters that generate at least one rotating optical beam and that can be used in a position location system.
2. Description of the Related Art
Local area position measurement systems have been developed that will quickly and accurately generate digitized three-dimensional position data. For example, U.S. Pat. Nos. 5,100,229, 5,110,202, 5,247,487, and 5,294,970, the contents of which are hereby incorporated by reference, describe such position measurement systems. Each position measurement system includes one or more optical transmitters that transmit substantially planar laser beams. Each system also includes a portable position sensor that detects the laser beams. As explained in detail in the above-mentioned patents, digitized three-dimensional position data indicating the location of the position sensor can be generated based on time intervals defined by the detection of the laser beams by the position sensor.
Accurate position measurement with these systems requires accuracy in the generation of optical beams. More specifically, each of the optical beams must have a constant and known shape and a constant angular velocity, or a known pattern of angular velocities through each complete revolution of the beams, as it is rotated through space about a rigidly mounted axis by a drive system. Consequently, the optical transmitters must be designed and manufactured with considerable care. Any unknown variation in the shape or velocity of the laser beams as they rotate degrades the accuracy of the position location system.
U.S. Pat. Nos. 5,461,473 and 5,579,102, the contents of which are hereby incorporated by reference, disclose an optical transmitter that will generate the optical beams used in the above-mentioned position measurement systems. As shown in FIG. 4, a laser emitter 112 generates a collimated laser beam that passes through the center of a spindle shaft 118 and is incident on a prism assembly 108, which divides the collimated laser beam into two laser beams. Each laser beam diverges along a plane but remains vary narrow in a direction orthogonal to the plane. Thus, the laser beams are considered substantially planar. A drive motor 116 rotates the spindle shaft 118 and the prism assembly 108 to rotate the laser beams. A roof mirror 122 reflects the laser beams so that they rotate about an axis perpendicular to the rotational axis of the prism assembly 108.
This optical transmitter is impractical for the consumer market because it is uneconomical to manufacture. In particular, the design of the optical transmitter requires many precision optical components that are expensive and difficult to manufacture. In addition, the optical transmitter has a complex optical path, which requires precise mounting and alignment of the optical components to prevent variations in the shape of the laser beams as they rotate. This optical transmitter also is rather large and heavy. Moreover, it requires a large and heavy battery when the transmitter is used in a portable application.
The present invention is directed toward reducing the effects of at least one of the above mentioned problems.
An embodiment of the present invention is directed toward providing an optical transmitter for use in a position location system that produces optical beams that rotate at a constant angular rate and have a constant shape as the beams are rotated.
An embodiment of the present invention is directed toward providing an optical transmitter for use in a position measurement and location system that can be manufactured efficiently and economically.
An embodiment of the present invention is directed toward providing an optical transmitter that is relatively small and light.
An embodiment of the present invention is directed toward providing an optical transmitter that has sufficient operational efficiency to permit the use of a small and light portable power source.
Additional features and advantages of embodiments of the invention may be apparent from the description that follows. Further advantages of the invention also may be learned by practice of the invention.
Briefly, in accordance with one aspect of the present invention, there is provided an optical transmitter. The optical transmitter includes a rotating head assembly, a rotary power source, and a signaling unit. The rotating head assembly includes a first optical source that generates a first optical beam that is narrow in a first plane and diverges in a known way in an orthogonal plane. The rotary power source is for providing power to rotate the rotating head assembly at one or more known angular velocities. The signaling unit is for emitting a synchronization signal at a specific rotational position of the rotating head assembly.
Briefly, in accordance with another aspect of the present invention, there is provided another optical transmitter. The optical transmitter includes a rotating head assembly and a rotary power source. The rotating head assembly includes a first optical source that generates a first optical beam that is narrow in a first narrow plane and diverges in a first known way in a first orthogonal plane. The rotating head assembly further includes a second optical source that generates a second optical beam that is narrow in a second narrow plane and diverges in a second known way in a second orthogonal plane. The rotary power source is for providing power to rotate the rotating head assembly at one or more known angular velocities.
Briefly, in accordance with another aspect of the present invention, there is provided a method of transmitting an optical signal. The method includes (i) providing a rotating head assembly having a first optical source, (ii) generating, with the first optical source, a first optical beam that is narrow in a first plane and diverges in a known way in an orthogonal plane, (iii) rotating the rotating head assembly, and (iv) emitting a synchronization signal at a specific rotational position of the rotating head assembly.
Briefly, in accordance with another aspect of the present invention, there is provided another method of transmitting an optical signal. The method includes (i) providing a rotating head assembly having a first optical source and a second optical source, (ii) generating, with the first optical source, a first optical beam that is narrow in a first plane and diverges in a first known way in an orthogonal plane, (iii) generating, with the second optical source, a second optical beam that is narrow in a second plane and diverges in a second known way in a second orthogonal plane, and (iv) rotating the rotating head assembly.
Briefly, in accordance with another aspect of the present invention, there is provided yet another optical transmitter. The optical transmitter includes a mechanism for generating an optical beam that is narrow in a first plane and diverges in a known way in a second plane, and a mechanism for rotating the optical beam. The optical transmitter further includes a mechanism for emitting a synchronization signal at a specific rotational position of the optical beam.
Briefly, in accordance with another aspect of the present invention, there is provided still another optical transmitter. The optical transmitter includes a mechanism for generating a first optical beam that is narrow in a first plane and diverges in a first known way in an orthogonal plane, and a mechanism for generating a second optical beam that is narrow in a second plane and diverges in a second known way in a second orthogonal plane. The optical transmitter further includes a mechanism for rotating the first optical beam and the second optical beam, wherein the first and second optical beams are in a fixed spatial relationship.
It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.